Offset printing plate clamp



Feb. 13, 1962 F. NEAL OFFSET PRINTING PLATE CLAMP I INVENTCR 7 0% M BY kFiled May 12, 1960 Ill. ll ll ATTORNEY l'l l I I i l I l l I l I I Illlullll Ir l l l I l l I I I l T I l l l III 3,020,842 OFFSET PRINTINGPLATE CLAMP Frank Neal, New City, N.Y., assignor to R. Hoe & Co., Inc.,New York, N.Y., a corporation of New York Filed May 12, 1960, Ser. No.28,573 2 Claims. (Cl. 101-4151) This invention relates to improvementsin plate clamps, and more particularly to clamps of this type such asare used for offset printing plates.

In offset printing machines, the printing plate is of relatively thin,strong metal, such as aluminum alloy or steel, and is tensioned aroundthe plate cylinder by suitable clamping means gripping its ends andoperating within longitudinal channels or bores formed in the cylinderand communicating with the cylinder periphery through a gap.

It is an object of the invention to provide a plate clamping mechanismof this character which allows simple insertion of the plate ends into arelatively small gap in the cylinder periphery and a positive grippingthereof by the clamping means regardless of the precise position of theplate edge with relation to such means, together with a rapid release.

A further object is to provide a mechanism of the character indicated,in which the plate ends require no special preparation such aspreparation for the incorporation of clamp engaging elements.

With these and other objects which will appear in the following fulldescription in mind, a mechanism embodying the invention in a preferredform will now first be described with reference to the accompanyingdrawing, and the features forming the invention will then be pointed outin the appended claims.

In the drawing:

FIG. 1 is a fragmentary section, partly broken away, of the platecylinder clamping mechanism, and is taken on the line '1-1 of FIG. 2;

FIG. 2 is a section on the general line 22 of FIG. 1; and

FIG. 3 is a detail looking in the direction of the arrow 3-3 of FIG. 2,showing a worm and worm wheel operating mechanism.

The plate cylinder body 1 has a generally cylindrical surface 2interrupted by a gap 3 which extends chordwise of the cylinder and at anangle about 45 to a radial or axial plane. A wall 5 of this gap makingan acute angle with the cylinder surface is joined to the cylindersurface 2 by a somewhat rounded nose 6 and takes the end 7 of the plate8, which is bent to the shape indicated prior to attachment to thecylinder, and serves to position the plate circumferentially. The otherend 9 of the plate lies against the other wall 10 of the gap which makesan obtuse angle of about 135 with the cylinder surface and is blendedtherewith in a gentle curve 11 as indicated.

While only the ends of the plate 8 are shown, it will be understood thatthe plate exends around the entire circumference of the cylinder 1.

The mechanism for gripping the plate end 9 comprises a block 12 slidablein a channel 1'3- having a wall 14 parallel to the gap walls 5 and 10and which supports the block 12. This block has a beveled nose portion15 having opposed parallel surfaces 16 and 17 spaced from the gap walls5 and 10 by somewhat more than twice the thickness of the plate. The gapwall 10 extends part way under the nose 15 as indicated and the plateend 9 is inserted in the space between the two into a recess 18 formedin the member 12. This recess contains a number of rollers 19substantially coaxial with each other and spaced along the cylinder, asindicated in FIG. 2, at convenient intervals, each roller havingassociated with States Patent 0 it two springs 20 which seat in bores 21in the member 12 and urge the roller outwardly of the cylinder. Oppositesurface 16, the nose 15 has a beveled surface 22 forming the oppositewall of the recess 18 and against which the rollers 19 are pressed bythe spring 20, so as to grip the plate end 9 between the rollers 19 andthe surface 16, as indicated in FIG. 1. The gap wall 10 terminates in anabutment 23 in position for engagement by the rollers 19 when the block12 is moved toward the cylinder surface. As is apparent, such movementof the block 12 beyond the point Where rollers 19 engage abutment 23will compress springs 20 and bring a lower point of the bevel 22opposite the roller, thereby releasing pressure of the rollers againstthe plate end 9, for releasing this plate end. Thus, movement from theplate clamping position of FIG. 1 of the block 12 to substantially thelimit permitted will release a plate gripped thereby and position theelement 12 for receiving any other plate end which may subsequently beinserted. Movement of the block 12 is accomplished and its position isdetermined by means of a series of racks 25 carried by this block andspaced along its length, adjacent the rollers 19, which racks areengaged by gear wheels 26 fixed to the operating shaft 27 journaled inthe cylinder. Shaft 27 carries at its end and outside the cylinder aworm whee128 which cooperates with a worm 29 mounted in a bracket 30secured to the cylinder. The worm shaft has an end 31 formed forengagement by a wrench. It will be apparent that by turning the worm 29,the block 12 may be moved (to the left in FIG. 1) to a positionreleasing a plate and readying the clamp for taking another plate and itmay also be moved (to the right in FIG. 1) in the opposite direction soas first to grip the plate inserted under the nose 15 and then tensionthe same to any required extent.

The mechanism for gripping the opposite end 7 of the plate isessentially similar and comprises a block 32 having a similar recess 18with walls 16 and 22 respectively parallel to the gap walls and slantedand having similar rollers 19 and springs 20 accommodated in bores 21,all as described in connection with the member 9. The plate end 7 isinserted past the nose 15 of block 12 and between the recess wall 16 ofblock 32 and the facing Wall 5 of the slot, in the manner shown in FIG.1, and this plate end is gripped and released by movement of the block32 in the same manner as described in connection with the block 12.Blocks 12 and 32 slide against each other and against the wall '14 ofthe channel 13 previously mentioned and opposite wall 33 thereof, thusbeing maintained in position with relation to the cylinder gap at alltimes. Elements 32 similarly are provided with rack segments cooperatingwith gear wheels 26 fixed to a second operating shaft 27 also providedwith a worm wheel 28 beyond the end of the cylinder body. As is evident,the rack, gear and operating shaft parts of the two ends of the platemay be, as shown, identical. Worm 29 which operates the block 32 issimilar to the worm 29 previously described but has a somewhat shortershaft due to the positioning of the parts in the cylinder.

While the clamping mechanism of the invention is primarily intended forattaching offset printing plates to their plate cylinders, it may alsobe used for attaching relief printing plates, where these plates havesupports or backing elements in the form of thin, flexible sheet metalmembers, and for fastening blanket or resilient elements, similarlysupported, to impression or other printing cylinders.

What is claimed is:

1. A plate clamping mechanism for printing machine cylinders comprisinga cylinder body portion having a slot at substantially 45 to thecylinder axial plane, a pair of clamping elements, means for mountingthe said elements in the said slot for movement independently of eachother, and comprising opposed parallel guiding surfaces supporting theelements slidably against each other, each element having a recess forreceiving a plate end, the said recess having opposed walls, onepositioned substantially parallel to the said guiding surfaces forsupporting the plate end and the other being beveled, a rollerpositioned between the two said walls for clamping the plate, a springwithin the recess for urging the said roller to wedge the same and aplate engaged thereby between the two said opposed walls, thus clampingit in the element, means for moving the said element between a plateclamping and plate releasing position and means engaging the roller inthe latter said position and holdingit back against the action of thespring to release the plate end, one of the said pair of clampingelements having a portion positioned beyond the other said clamping ele-References Cited in the file of this patent UNITED STATES PATENTS1,159,941 Hohner Nov. 9, 1915 1,937,119 Krantz Nov. 28, 1933 FOREIGNPATENTS 387,695 Germany Ian. 2, 1924

